Oil and Gas Found in Rocks? Oil Shale and Cracking


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What is oil shale fuel? Is it comparable to gasoline? Image by arfelfin

Oil and gas are of critical importance to most economies, but supplies wax and wane in response to issues with oil-rich nations, and our own drilling concerns. The dependence on these fossil fuels makes the raw materials important for both political and military reasons.

In seeking local energy reserves, we have, on occasion, turned our collective attention to oil shale rock deposits.

What is Oil Shale?

Oil shale is a fine-grained form of sedimentary rock that contains a considerable amount of organic material. We can convert the organic material, or some of it, into a kind of fuel oil called shale oil.

The largest single source of oil shale in the world is located across Colorado, Utah and Wyoming. These oil shale deposits are also associated with natural gas reserves.

Oil Shale Rock Characteristics

Approximately 60 to 90 percent of oil shale consists of mineral deposits, including silicates, aluminosilicates, and carbonates. Sometimes sulfide traces are present. Scientists believe that the organic substances that form the origins of shale oil come from bacteria, plankton, algae, and land plants. The presence of sulfides in some oil shale suggests anoxic water (water without oxygen) was present during its formation. Shale deposits can be assayed for quality using the Fischer Assay method.

‘Cracking’ Shale for Organic Exudate

The current theory is that oil shale formed under the influence of heat and pressure and bacterial action. Under these influences, organic substances originally present broke down into a waxy, solvent-insoluble fraction called kerogen, in addition to a black, tarry, solvent-soluble substance called bitumen. Kerogen accounts for about 90 percent of oil shale’s organic content. Since there is so little solvent-soluble material in oil shale, when we want to get to it, we use a process called destructive distillation, also called cracking.

Characteristics of Shale Oil

MIT lists three types of shale oil. The kind most suitable for stand-alone fuel is high in its hydrogen-to-carbon ratio. Another type of shale oil possesses a high oxygen-to-carbon ratio. This means we must combine this type of oil with hydrocarbon-rich material to make make it more well suited for fuel.

Shale Oil vs. Crude Oil – Cracking or Drilling?

Again and again, during times of economic disparity, we find the subject of shale oil approaching as businesses and individuals reconsider our need for fuel of all sorts. Although shale oil is available, it’s important to consider the differences, from environmental issues to our ability to use the oil easily. Businesses and consumers would need to make adjustments to the current technology to utilize shale oil, for example.

It is also less expensive and less damaging to the environment to obtain crude oil than it is to obtain shale oil via cracking. Although there may be less damage to the environment via crude oil drilling, the economy may demand more shale oil.

For these reasons, it is likely to remain right where it is for many of us, in the rocks below.

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